White spruce

White spruce: how do you recognise it?

Habit

The species: conical tree about 20 m tall and 6 m wide. ‘Conica’: a dense, regular cone, usually 2–4 m tall and 1–1.5 m wide.

Needles

Stiff, 1.2–2 cm long, square in cross-section, blue-green with a waxy bloom; sharp scent when crushed.

Cones

Cylindrical, 4–6 cm long, hanging; green at first, later light brown, with thin, flexible scales.

Bark

Thin, grey-brown and flaking.

Roots

Shallow and widely spreading: avoid compacted soil and water regularly in the first years.

Plants: April–May and September–October

Why grow it?

• Extremely hardy, to about −45 °C: a tree that copes with every Belgian winter.
• Evergreen, with blue-green needles all year round.
• The dwarf form ‘Conica’ gives a neat, conical structure in small gardens, pots and front gardens.
• Low maintenance: no pruning needed.
• The species itself makes a good windbreak or specimen in a large garden, with dense branches that shelter birds.

White spruce: where does it grow best?

• Sun to light partial shade; in full sun it stays the densest.
• Ordinary garden soil: sand or loam, acid to neutral, well drained.
• Normally moist: it does not tolerate long drought or wet feet.
• Do not put ‘Conica’ against a sunny wall, where it gets hot and dry, but in an airy spot.
• Allow 6 m width for the species; 1–1.5 m for ‘Conica’.

Light

Sun and partial shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal

Size

20 m tall, 6 m wide

Hardiness

Hardy (to -45 °C)

Goes well with

• Heather: Low, colourful planting on the same acid, well-drained soil.
• Winter heath: Flowers in winter and early spring; lovely in pots beside a conical spruce.
• Blue fescue: Blue-grey tufts that match the blue-green needles.
• Stonecrop: Sturdy and drought tolerant as underplanting in a sunny spot.

White spruce: when and how to plant it?

Plant in April–May and September–October.

1. Plant in April–May or in September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole twice as wide as the root ball and just as deep. Loosen the sides so the roots can grow out easily.
3. Set the plant at the same depth as in its pot or root ball: the root collar stays at soil level.
4. Give the species 5–6 m from other trees and buildings; plant ‘Conica’ 1–1.5 m from neighbours or a path.
5. Water generously straight away, even if it is raining.
6. Spread a layer of bark or leaf mould mulch around the base, keeping it clear of the trunk.

Care

Water

In the first year, water generously every week in dry spells. Later too in long dry periods: drought and heat are the main causes of spider mite.

Feeding

In spring, a little compost or an organic fertiliser for conifers. Do not overfeed.

Mulching

Bark or leaf mould keeps the shallow roots cool and moist.

Spraying

In warm, dry weather, spray ‘Conica’ with a hose now and then, including beneath the branches: this keeps spider mite away.

Checking

In summer, look for fine webbing and pale or brown needles on the inside of the plant.

Tip: Do not put ‘Conica’ against a sunny wall, and water in dry spells: spider mite is the main problem. In summer, check beneath the branches and spray with a strong jet of water.

White spruce: when to prune it?

When: It does not need pruning: the shape stays neat by itself. Only remove dead or damaged branches if necessary.

How:

• Cut dead or damaged branches back to the trunk or a side branch.
• On the species, remove a double leader and leave one strong leader.
• On ‘Conica’ it is better to do nothing: the dense conical shape does not recover after hard pruning.

Caution: Never cut into bare wood without needles: a spruce will not regrow from it.

Pruning calendar and basic rules

Propagation

Seed

Mainly for the species: collect the cones in autumn, let them dry and shake out the seeds. Sow them in spring in pots outdoors, after a cold period over winter.

Cuttings and grafting

‘Conica’ and other selections are propagated by nurseries from cuttings or by grafting; seedlings do not come true to the parent plant.

White spruce: how does it get through the winter?

Hardy to −45 °C.

• Very hardy, to about −45 °C: no protection is needed.
• In a pot: put the pot in a sheltered spot and wrap it in hessian so the roots do not freeze. Water in dry, frost-free weather, because evergreens keep losing moisture.
• Late winter sun can scorch the sunny side of ‘Conica’; hessian or a spot with some shade helps.

Diseases and pests

• Spider mite: Fine webbing and pale, dried-out needles, mainly on the inside, in heat and drought. Hold a sheet of white paper under a branch and tap it: tiny moving dots are mites. Spray regularly with a strong jet of water and water generously.
• Brown needles: Needles turn brown from winter sun or from drying out in frost. Water in dry winter weather and shelter from late winter sun.
• Root rot: Yellow, drooping branches and a dying crown in soil that stays wet for long. Provide well-drained soil.
• Aphids: Now and then on young shoots, sometimes with sticky honeydew. Spray them off with water; ladybirds help.

Through the year

• January: Rest. Protect pots from frost and water them in dry, frost-free weather.
• March: Late winter sun: protect pots and young ‘Conica’ with hessian if needed.
• April: Plant. Give compost or a fertiliser for conifers.
• May: Plant. Apply mulch. Light green new shoots.
• June: Water in dry weather. Check for spider mite.
• July: Spray in dry, warm weather. Water.
• August: Water in dry and hot weather.
• September: Plant. The cones ripen.
• October: Plant. Water new plantings.
• November: Move pots to a sheltered spot or wrap them against frost.
• December: Rest. Water pots in dry, frost-free weather.

Did you know?

• ‘Conica’ was found in 1904 at Lake Laggan in Alberta (Canada), as a chance dwarf form growing in the wild; hence the name dwarf Alberta spruce.
• White spruce grows right up to the northern tree line in Alaska and Canada.
• The species name glauca means ‘blue-grey’ and refers to the waxy bloom on the needles.